Patent Publication 1 (Japanese Patent No. 2,946,323) discloses a compound needle including a needle body having blade grooves, and a slider including two blades that are movable back and forth in the blade grooves. At the front ends of the two blades of the slider, tongues are provided. By the forward movement of the slider, the tongues close a hook at the front end of the needle body. By the further forward movement of the slider, the tongues move beyond the hook for loop transferring or the like. Further, the two blades are overlapped with each other, and accommodated in longitudinal grooves provided in a slider jack. A butt of the slider jack is manipulated for moving the blades back and forth. The base end of the needle body is attached to the needle jack, and the butt of the jack is used for manipulating the needle body. Further, in order to prevent the undesirable movement of the slider by the movement of the needle body, one of the two blades has an expansion at a position in the longitudinal groove of the slider jack. The expansion contacts the side surface of the needle groove of the needle bed. By the frictional resistance, the undesirable movement of the slider is prevented.
Patent Publication 2 (WO 01/31102A1) discloses studies about the sliding resistance at the time of the forward movement of the tongues of the compound needle beyond the hook of the needle body, and expansion of the space between the blades when the blades are widened toward the left and right by the hook. Patent publication 2 proposes to provide a partition wall between the blade grooves of the needle body, and dispose the two blades on the left and right sides of the partition wall, respectively. As a result, when the tongues move forward beyond the hook, instead of widening the two blades at a large angle, the angle of widening the blades is reduced by the partition wall to reduce the size of expansion toward the left and right. Further, since there is a gap corresponding to the partition wall between the blades, the sliding resistance between the hook and the blades is small. Further, the partition wall functions to guide the two blades, and scrub away the fiber debris entered between the blades.
In the compound needle disclosed in Patent Publication 2, a gap is formed between the two blades projecting from the blade grooves. When the blades hold a knitted loop, a force in a lateral (left or right) direction may be applied to the blades from the knitted loop. For example, when the blades hold the knitted loop at any of the opposite ends of the knitting fabric or when the blades hold the knitted loop which has been subjected to racking, since the knitted loop is pulled in the lateral direction, the force is applied to the blades. As a result, the blades may be warped undesirably, and it may not be possible to hold the hook between the two blades. Further, the two blades may be deviated toward one side of the hook undesirably. These problems may cause errors in knitting.